The Max Potion (Japanese: まんたんのくすりTank-Filling Medicine) is a type of medicine introduced in Generation I. It can be used during or outside of a battle to restore a Pokémon's HP.
In Pokémon GO, the Max Potion can be used to completely heal a Pokémon's HP. It can only be used outside of battle, including through the Gym interface immediately before a challenge.
Max Potions can be obtained starting at level 25 by searching PokéStops or Gyms. Max Potions are also available as rewards for leveling up starting at level 25. Max Potions can also be purchased with PokéCoins at the Shop.
In the anime
Max Potions in the anime
Max Potions debuted in SM061, where Ash and his classmates received a medical kit containing three of them, among other healing items, to be used during their Ultra Guardian missions.
This card allows the player to heal all damage from one of their Pokémon. The player then discards all Energy attached to that Pokémon.
Trivia
In GenerationsI and II, Max Potion was programmed to only heal 999 HP, rather than restoring the HP to maximum. However, since the highest possible HP a Pokémon can legitimately have in these games is 703 with a level 100 Chansey (in Generation I) or 713 with a level 100 Blissey (in Generation II), this is not an issue.
Likewise, in early releases of Pokémon Platinum, the Max Potion was mistakenly programmed to only heal 1,000 HP of damage (though a Pokémon with higher than 999 HP is not legitimately possible). This was fixed in later versions, which heal HP to 100%.